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Posted on October 11th, 2019
Following increased awareness of health risks associated with PFAS, the EPA released a Health Advisory in 2016 concerning PFOA and PFOS. This set the health limit for lifetime exposure in drinking water at 70 parts per trillion (ppt) and the minimum on-site concentration required for further assessment at 40 ppt.
Although not legally-binding, the Department of Defense chose to follow these guidelines in assessing the risk of PFOA and PFOS contamination on military bases. A number of US states decided upon their own minimum safety standards for PFAS in drinking water, in some cases including more than just two members of the class.
The reason for this becomes apparent when considering the murky nature of environmental and toxicological research in general. There is no uniform set of criteria by which all labs assess the potential hazards of a substance. For example, some might look into the connection between PFOS and liver damage and come up with a relatively high threshold for safety, while others would do the same for immune system deficiencies and set the minimum acceptable limit very low.
As a side-note, the lowest concentrations of PFOS and PFOA that can have any toxic effect - also called a "toxicological limit" - have been shown to act on the immune system and mammary gland development in mice and dogs at doses as low as 1 ppt. The EPA used neither of these studies in their advisory, despite consulting a large body of work.
Unsurprising, the EPA Health Advisory was quick to draw criticism from both governmental and independent sources, including the C8 Panel Study, the Science Panel Website, the World Health Organization, and the International Agency for Research on Cancer.
Most significantly, the federal Agency for Toxic Substances and Disease Registry (ATSDR), a part of the CDC, released a 2018 document in which it recommended minimum harm limits for PFOS and PFAS ten times lower than those set by the environment agency. The ATDSR also included two other common PFAS in their report which have been shown to be responsible for adverse health effects, although not to the same extent as PFOS and PFAS.
According to the NRDC website, the draft's release might have even been delayed by certain state actors, out of concerns that such strong disagreement from another federal institution might negatively affect both the DoD's and EPA's public image.
Even the lower figures suggested by the ATDSR are considered insufficiently prudent by organizations like the NRDC, who declared the report "a good start", but in need of improvement, citing that studies placing the minimum toxicological endpoint at 1ppt weren't given enough attention.
Their own recommendations place the maximum limit for PFAS and PFOS along with two other intoxicants in the family (PFHxS and PFNA) at 2 ppt in drinking water and around twice that for the safer GenX.
However, values so low might just be too impractical to aim for, as most of the common filtration methods used to remove PFAS aren't 100% effective, and reverse osmosis techniques which basically distill the water pose their own problems. Even states with particularly stringent regulations regarding PFAS are considering more lenient thresholds. The most cautious in this regard is currently Michigan, whose state legislature set the maximum contaminant level for drinking water at 9 and 8 ppt for PFOA and PFOS respectively, additionally including under regulation three other PFAS chemicals commonly associated with local industrial activity.
Minnesota was one of the first to take note of the PFAS problem back in 2006 and set a relatively high guidance level of 35 ppt for PFOA and 15 ppt for PFOS, but this was still a lot lower than the figures the EPA was considering at the time.
New York, New Jersey, California, Vermont, and Massachusetts complete the list of states who either proposed or adopted maximum contamination levels that are significantly below what the EPA deems safe for the nation as a whole.
Although the amount of research available has grown tremendously in the past years, most data we have on PFAS comes from toxicology studies. These are conducted on animals in a controlled lab setting and usually have a very narrow focus - which is fine - but precludes them from offering a holistic picture of the real-world impact that their object of study might carry. This is where epidemiological research comes in.
DuPont was recently forced under a lawsuit settlement to fund a study of 69,000 Mid-Ohio Valley residents who were using drinking water sources with at least 50 ppt of PFOA for at least a year. Researchers found this cohort to be suffering from a myriad of health problems associated with PFAS such as high cholesterol, thyroid disease, ulcerative colitis, pregnancy-induced hypertension, testicular cancer, and kidney cancer, at a rate significantly greater than the general population.
Important to note that the EPA safety advisory of 70 ppt refers to lifelong exposure and the only time limit placed on the Ohio cohort was one year. PFAS have been shown to have a toxic effect on children in significantly lower concentrations than in adults, and the fact that it accumulates in the body makes the timescale for exposure all the more important when assessing its potential as a pathogen.
For example, New Jersey adopted its relatively low threshold for drinking water safety of 14ppt after studies revealed their state population already had a near-dangerous amount of PFAS in their blood.
There is a clear trend where the toxicology safe limits placed on PFAS seem to lower as more data is collected on the chemical. The more we know about it, the more harmful it looks. EPA advisory levels also follow this trend, but by some years behind most of the scientific community. The sooner they catch up, the better.